diff -r 000000000000 -r f90c822e73f8 src/share/vm/memory/genRemSet.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/memory/genRemSet.cpp	Wed Apr 27 01:25:04 2016 +0800
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "classfile/classLoaderData.hpp"
+#include "memory/cardTableRS.hpp"
+#include "memory/genRemSet.hpp"
+
+// This kind of "BarrierSet" allows a "CollectedHeap" to detect and
+// enumerate ref fields that have been modified (since the last
+// enumeration.)
+
+uintx GenRemSet::max_alignment_constraint(Name nm) {
+  assert(nm == GenRemSet::CardTable, "Unrecognized GenRemSet type.");
+  return CardTableRS::ct_max_alignment_constraint();
+}
+
+class HasAccumulatedModifiedOopsClosure : public KlassClosure {
+  bool _found;
+ public:
+  HasAccumulatedModifiedOopsClosure() : _found(false) {}
+  void do_klass(Klass* klass) {
+    if (_found) {
+      return;
+    }
+
+    if (klass->has_accumulated_modified_oops()) {
+      _found = true;
+    }
+  }
+  bool found() {
+    return _found;
+  }
+};
+
+bool KlassRemSet::mod_union_is_clear() {
+  HasAccumulatedModifiedOopsClosure closure;
+  ClassLoaderDataGraph::classes_do(&closure);
+
+  return !closure.found();
+}
+
+
+class ClearKlassModUnionClosure : public KlassClosure {
+ public:
+  void do_klass(Klass* klass) {
+    if (klass->has_accumulated_modified_oops()) {
+      klass->clear_accumulated_modified_oops();
+    }
+  }
+};
+
+void KlassRemSet::clear_mod_union() {
+  ClearKlassModUnionClosure closure;
+  ClassLoaderDataGraph::classes_do(&closure);
+}